Bowl mill



April 15, 1941. LYKKEN 2,238,743

BOWL MILL Filed May 15, 1938 3 Sheets-Sheet l [NVENTOE HENRY 6. L Y/\ EN g fit "*1 H. G. LYKKEN April 15, 1941.

BOWL MILL Filed May 13, 1938 3 Sheets-Sheet 2 [/v VENTOE HENRY 6. L YKKEN 6 MM H. G. LYKKEN April 15, 1941.

BOWL MILL Filed May 15, 1958 I5 Sheets-Sheet 5 JNVENTOE HENRY 6. L YKKEN yfim4 l/ t ATTO N YJ' tial'ly horizontal axis.

Patented Apr. 15, 1941 Henry Gdakken, Minneapolis, mm. i Application 13, 1938. No. 207,859 '1 (CI. as-a) invention rests to pulverizing and grinding mills of the type in which material to. be reduced in size is subjected to the interaction of an activated mass ofmetallic, balls, flint pebbles, or

v the like,into which the material is fed and subsequently removed when suillciently reduced in size The interaction and activation of'the mass has heretofore been accomplished by revolving the mass in a tubular container, about a substan- In the standard ball or tube mill the ball charge moves only in the direction oi rotation, and there is no axial movement or displacement of the ball charge itself. As a result there is a lack of length.-

wise distribution of the material to be reduced in the ball charge, too much material being present at the feed end and too little at the discharge end. The movement of the charge is a minimum distance in the plane perpendicular to the axis of rotation, or otherwise stated, the axis of the cascading oi the charge is parallel to the axis of rotation.

I have discovered that superior results from the standpoint of quality ofgrind, capacity of the 'mill, and amount of power consumed in grinding can be accomplished if, each particle of the mass and the mass is caused to move in a closed path which lies across the mill and at the same time caused to moveaxially of the mill. In order to obtain this motion I cause the activation of the mass to be carried out in a bowl-shaped mill, such as a closed bottom cylinder, which is revolved about an axis'inclined to the horizontal. It is, therefore, an object of the present invention to provide an improved mill in which the activation of the mass is about a closed path of motion across and lengthwise of the mill.

In the present invention the activation of charge is carriedout in a bowl-shaped container which is revolved about an inclined axis. The bowl .is loaded nearly full at the bottom, and the loading tapers ofi to zero, at the upper or open and the movement of the material per revolution increases the grinding action and efiiciency. V

v There is betteriiberation of the finished productfrom the charge, due to the axial movement which avoids excessive reduction, and since the center of gravity of the mill is closer to the axis of rotation than is the usual ball or tube mill, de-

creased power is necessary for startingand runto metal wear uponthe grinding media and liner a material being processed will take place and the the' circulating cascading effect of the material by which the individual particles are moved endwise of the mill as well as transversely.- In this .way

the charge is continuously, cascaded'from end to, I

material may be dividedthereby into particles of various sizes and grades. It is therefore a further object of the-invention to provide a combined mill and classifier, and to provide a method and means ofgrinding and classifying material.

Other and further objects are thoseinherent and implied by the invention set forth in the specification, claim and drawings.

The invention is illustrated with reference to the drawings in which- Figure 1 is a cross-sectional view in elevation of one modification of the present invention.

Figure 2 is a cross-sectional view along the line 22 of Figure l. v

Figure 3 is an elevational view partly in section of a mpdified form of the invention.

Figure 4 is an'elevational view partly in section of another modification of the invention.

Figure 5 is an elevational view partly in section of a modification of the invention in which a liquid is used as the classifying medium.

Figure 6 is an elevational view partly'in section showing another modification of the invention in which a liquid is usedas the classifying medium. The milling and classifying machine of the present invention, illustrated in Figure 1, comprises a bowl-shaped chamber generally desigof the material in the charge, greatly increases. 1

the grinding eificiency and capacity of the mill.

This makes possible increased-loading of a given inated Ill, which is mounted for rotation upon an angularly positionedjournal generally designated ii. The bowl-shaped chamber II is preferably of circular cross-section, as shown in Figure2,

. 2 but in some instances it is desirable to make the chamber of polygonal cross-section as hereinafter pointed out. n

The chamber .III is constructed of an outer shell ll of steel plate or other suitable material, and a cylindrical liner I! of wear-resistant material'. Liner I! may be of one piece or a number of segments and may be of thick cross-section'toward the lower end l3 of the chamber and gradually decreased in thickness toward the upper end 14. The liner [2 does not extend to the bottom of the shell I I but is joined by a cast endclosure plate I! which serves toclose the end of shell I I so as to form the bowl-shaped chamber. ill.

The end-closure plate I I is provided with a plurality of radial protuberances l8 which as subsequently described, serve to lift the mass of grinding media and material to be ground, and thus activate the mass. The end-closure plate I5 is also provided with an integrally cast boss 16A which protrudes into the chamber, and a stub shaft l1 upon which the entire device rotates. A large ring gear I3 is attached to the bottom of the bowl l0 and meshes with a pinion gear (not illustrated) which serves to rotate the chamber. The angularly shaped journal bracket 2|! is provided with an anti-friction bearing 2| having a thrust section 22 which carries the axial load during the rotation of the mill. 30

The upper end of cylindrical shell I l is provided with a tire 25 which rotates upon a plurality of rollers 26 only one of which is illustrated. It is understood that a number of rollers are provided as required, in order adequately to distribute the load and steady the mill.

The upper end of the cylindrical shell H is closed by a conically shaped cap 30 which is. preferably welded to the shell II at the junction 3|. The small end of conically shaped cap 30 is provided with a cylindrically shaped extension 33 which has an outwardly extending flange 34. All of these parts rotate with the mill. I

Adjacent the upper end of the mill there is mounted a unit generally designated in, which serves to introduce the material to be comminuted and the classified fluid into the mill and to remove the classified comminuted material from the mill. Unit is mounted on a pedestal 4i and is stationary with respect to the mill.

Unit 40 comprises a jacket 42 which has a protruding cylindrically shaped section 43 fitted to the cylindrical extension 33 of the mill. The two parts 33 and 43 are fitted with small clearance so that when the mill is rotated the outward passage of the classifying fluid and the comminuted material will be prevented. The sealing eii'ect between cylindrical section 33 of the mill is enhanced by a flange 44 which is mounted on cylinder 43 so as to overlie flange 34 of the mill. Any other seal may obviously be used between the unit 40 and the mill section, the object being to provide a rotating fit between the two units 65 and at the same time maintain the clearance sufilciently small so as to prevent the outward flow of classifying fluid and material at that point.

A central tube 45 is mounted in the cylindrical housing 42 and p ojects into the mill. The inner projecting en 46 of the tube 45 carries a conically shaped classifier head 41' having a flange 48 which parallels shell II but is spaced from it so as to provide an annular passageway 49 between the upper end 14 of liner l2 and the 75I flange 48. Passageway 43 is continued toward the apex of the mill, and increases in width.

Unit 4| is provided with a horizontal tube 50 and feed screw SI for the introduction of solid material into the mill,'and also with a duct 33 for the introduction of classifying fluid which in this instance is a gas such as air.

During operation the mill is loaded with a charge of grinding media such as hardened steel balls, flint pebbles, or the like, and the material to be comminuted is introduced by means of feed screw 5| until a suflicient mass of material and grinding media is present in the mill so that it fllls the bowl portion id to level 55 when the mill is at rest. It is assumed that the mill is rotated clockwise as viewed-in Figure 2, or so that the top of the mill approaches the observer in the view Figure 1. When the mill is thus rotated the charge of grinding media and material is lifted due to its contact with the liner I! of the mill and particularlydue to the contact with radial lifting vanes IS. The material is carried upward until it reaches a high level away from the observer (as viewed in Figure 1), represented by the line 36, and a low level toward the observer, represented by the line 51.

When the material and grinding media are rotated upwardly with the mill the motion of an individual particle is in a plane perpendicular to axis 60. This motion may be represented by the vector GI and may be considered as having a horizontal component of motion 62 and'a vertical component of motion 63. Hence as the mass is being lifted each particle of material and grinding media moves toward the right in an amount represented vectorially by the arrow 82. As the particles of material and grinding media reach the level of line 56 (away from the observer, as viewed in Figure 1) they fall downward to the left. This motion may be represented by vector 65 and may be considered as having a downward movement represented by the vector 66, and a horizontal movement to the left, as represented by the vector 61. Thus for each rotation of the mill the mass of media and material is moved axially of the bowl about a closed path. The material is hence circulated axially of the mill as it is tumbled upon itself within the mill. This effect results from the inclination of the mill.

I have discovered that numerous advantages result when using a mill of the present invention, among which are the following: First, the ratio of the weight of the material to the weight of the grinding media'is much higher than in previous ball mills, and there is accordingly much less wear on the mill and power consumed per pound of finished material. Second, the quality of the ground material is enhanced because the grinding effect is largely due to attrition. Third, the power necessary to start the mill is less than in horizontal ball mills.

As the material is reduced in size by the action of the grinding media, it is removed from the mill by a current of classifying fluid which in Figure 1 may be air or other gas. The gas is introduced through the duct 53 and it then travels in the direction of arrow HI, through the space between stationary cylindrical member 43 and the member 33 of the mill, and thence through the space 49 and into the mill, as shown by arrow H. The gas then sluices through the mill and raises the fine particles of material and carries them upwardly through cylinder 40, in the direction of arrows I2. The only material which is removed from the mill is that which is flne enough to be carried by the current of classifying gas, the coarse material being left in the mill for further reduction.

The influx of classifying gas may be regulated in any desired amount by a vane I in the inlet duct 53 and the introduction of material to be ground may likewise be regulated by the rate of rotation of feed screw ii. The rate of flow of the classifying fluid through the mill in part determines the size of the particles of reduced material which may be lifted upwardly and through tube 40. By changing the rate of'feed of material and classifying fluid to the mill it is thuspossible to vary the size of the grind within wide limits.

In Figure 3 there is illustrated a modification of the mill shown in Figure l which is the same in all respects except for the means of introducingthe material to be comminuted and the classifying fluid. In Figure 3 a unit generally designated 80 replaces the unit 40 of Figure 1 and consists of an elbow-shaped tube I having a stationary flange 02 and a cylindrical portion 03 which cooperate itO form a fluid-tight connection with the rotated flange l4 and cylindrical portion II of the mill. Unit 00 includes an axial vtube II through which the classifying fluid and and reduced material.

The operation of this modification of the invention is analogous to that described above with reference to Figure I, particularly as to the circulation of material and the charge of grinding media within the mill. As the material to be comminuted is reduced in size it is picked up by the classifying fluid which impinges upon the activated mass in the direction of arrows II. The flne particles are lifted like dust and carried upwardly in the direction of arrows 01, through the space 00 between members 02 and tube II and thence outwardly in the direction of through the outlet port It.

In this modification, as in the modification shown in Figure 1, the rate at which the material and classifying fluid are introduced into the mill may be regulated by any suitable means and the amount of reduction of the material accordlngly regulated as desired.

In the modification shown in Figure 4 the which rotate with the mill and thus prevent the outflow of the classifying fluid at the Junction of these elements.

In operation material to be ground is introduced through small tube 00 in a regulated amount and classifying fluid suchas air or other gas is introduced through tube I05 and flows through the space I02 and along the path of the arrows H0 and H2 into the mill. Since the mill is loaded to a level which extends to near the upper edge I 4 of liner I2, some of the air or other classifying gas is forced through the activated mass at the upper portion of the mill and raises a cloud of reduced material which is then driven along the path of arrows III and I through outlet space I00. By this means it is possible to drive larger particles from the mill than is possible in the modifications illustrated in Figures 1, 2 and 3. In the mill illustrated in Figure 4 the circulation of the mass of grinding media and material within the mill is substantially the same as that described with reference to Figure 1.

In the modification shown in Figure 5 the mill is adapted to be used with a liquid classification media and the mill is accordingly not closed at the top as shown in Figures 1, 3 and 4 but is provided with a weir plate I20 by which the outflow of classifying liquid is regulated. In this mediflcation the mill is provided with a stationary tube I22 which extends into the body of the mill. The classification liquid and material to be comminuted are introduced through. tube I22 and the material is reduced in the presence of the liq uid, the circulation within the mill being analogous to that described with reference to the previous modifications except that the diiference between the high and low levels of the activated mass is not usually as great as when the reduction is carried on under dry conditions. This, however, depends upon the cohesiveness of the material being comminuted.

As the material is reduced in size it is more maintained in'suspension and as a con: sequence is carried-over the lip I23 of weir plate I" with the outflow -,of classifying fluid. V The larger, particles of material settle more rapidly and-are accordingly returned to' the activated *mass ofgrindingmedia and material; The partiper, portion of the bowl is provided with an air jacket, generally designated 00, which extends downwardly along the cylindrical shell II to any and liner I2 are pierced by a number of air inlet ports 02 for the passage of air from the jacket into the bowl. In this modification of the mill the conical section 20 which rotates with the mill is terminated at the point 92 where it joins stationary cylindrical tube 01 of the unit, generally designated 0!.

Unit 0! consists of three concentric tubes 00, l1 and 0.. Tube 00 is of small diameter and is provided for the introduction of material tobe comminuted. Tube 01 is of a diameter sumciently large that a space I" is provided for the outward flow of the classifying fluid and reduced material. Tube 00 is likewise sized so as to pro-' vide a space I02 for the'inflow of classifying flljild. It will be noted that tube ll is joined at point I02 to member 01 and that inlet tube III is procles ofmaterial remain'in the mass 'of'grinding media untilithey are sufllciently reduced insizeto ,be carried over the weir: plate by. the classifying- .liquid'. ItIisnnderstoom-ef course, that a steady flow of classifying fluid and material ismaintainedj through the' mill. The rate of flow and .theproportion' 'ofciassifyins-medium to mate- 'rial-may be regulated as desired to vary the size .oithegrinm Inthe'inodiilcation is provided with a 'weir' plate I20 which is the same as that described in Figure 5 and with an internal classification plate I25. The mill isalso provided with a stationary sluiceway I28 in addition totubel22. r

modification of the invention the reduced .rnaterial is" classifled and removed from ,themill "in two flows as follows: The lighter porvided for inflow of classifying fluid. 'mbe .u and flange III, which is mounted'upon it,-flt

with the'cylindrical portion Ill and fl ar'igeiilli .tions of; f the. material which remain suspended at, thej-surfacelevel I 24 of'the classifying fluid arec rtied over the edge [22 0f weir plate I20 as described with r'eference to the =m'odiflcati'on in li 'igu're'b, The somewhat coarser material setties between'weirplate I20 and theclassiflcation plate III and is carried upwardly as the mill rotates reaches an elevated position I21 at shown in Figure 6, t.he mill which point it tells into sluiceway I26, whence it drains downwardly from the mill. In this way the material is automatically classified into the iine and coarse sizes 'as it is removed from the mill. The circulation of the activated mass of grinding media and material within the mill is in this modification substantially the same asthat described with reference to Figures 1, 3 and 4 except that the difference between the high and low levels is not as great as in the dry grinding procedures. If desired a plurality of vanes (not shown) may be provided between the weir plate I20 and classification plate I25 so more readily to lift the material to a position above sluiceway I26.

In all of the foregoing mills the angle of inelination of the bowl may be varied as desired to suit conditions. The more nearly horizontal the mill is mounted the less will be the amount of axial circulation, and the greater the inclination the less will be the transverse circulation. I .have foundthat good results are obtained when the axis of the mill is substantially thirty degrees to the horizontal but I do not wish to restrict myself to this anzlllarity.

As previously stated, the cross-section of the mm may be circular or polygonal, as desired; In some instances it is desirable to use a triangular or square cross-section, or a cross-section having 6, 8 or 10 sides.

Other modifications may obviously be made without departing from the spirit of the invention described, and claimed as follows.

I claim as my invention:

A mill for grinding and pulverizing of material introduced thereinto, and for classifying and separating of such pulverized material comprising a bowl-shaped chamber having a closed bottom and upwardly extending walls, means mounting said chamber for rotation about an inclined axis with the open side of the chamber directed upwardly, and means for supplying a fluid to the chamber and for withdrawing the fluid laden with pulverized material from the chamber, the bottom of the chamber being provided with a central upwardly extendin domeshaped protuberance and a plurality of radial vanes around and extending from said protuberance.

HENRY G. LYKKEN. 

